The computerization of medical equipment and clinical chemistry equipment has resulted in numerous malfunctions due to inadequate quality of AC power. The AC power system in the Clinical Center was designed in the 1960's before the advent of computerization of equipment. We have witnessed malfunctions of respirators and clinical chemistry equipment used to analyze blood and urine samples from patients. The malfunctions have been related to voltage sags, surges and transients. In some cases they were due to improper selection of power conditioning devices such as surge suppressors and uninterruptible power supplies. We have tested a number of power conditioning devices, and along with manufacturer recommendations, have solved numerous power quality problems. We have selected several surge suppressors which can pass the stringent leakage current requirement of hospital equipment. Additionally, we have selected several uninterruptible power supplies and transformer power conditioners able to cope with the frequent voltage sags encountered in the hospital. To assure new medical equipment can function properly without extra power conditioning we participate in evaluation of clinical trials where equipment is tested prior to purchase.